The invention pertains to an impeller made from a sheet-metal disk and having a plurality of blades which are formed by cuts in the sheet-metal disk and are bent out of the plane of the latter.
Such an impeller is known (DE-OS 15 03 633). The known impeller is made from an approximately circular sheet-metal disk by making cuts into the latter and by bending the blades thus produced out of the plane of the sheet-metal disk by ninety angular degrees to one side or the other.
Although such prior-art impellers can be produced at low cost in the manner described above, they have two considerable disadvantages. One disadvantage is that only straight, outwardly extending radial blades can be made on the impeller in the manner described above. If the blades are to be only slightly curved, an increased expense caused by tools and material (e.g., material having special deep-drawing properties) is required. By this method, only slightly curved blades can be manufactured.
Since in the case of the prior-art impeller, the blades are bent out of the area of the impeller, only a limited area of the sheet-metal disk is available for the effective area of the blades, because for the folding step which is required when the blades are being bent, a given area is necessary where the sheet-metal disk is held.
If the prior-art impeller is to deliver a greater quantity of air, it is necessary, due to its unfavorable aerodynamic properties, either to drive the impeller at a high speed or to increase its diameter.
Both measures require a considerably higher driving power. Naturally, they also cause a considerably increased noise level. Since such blowers are predominantly used in electric stoves as circulation blowers, the motor is already at its limit of capacity, due to the high ambient temperature. A motor with a higher capacity adds to the expense of the entire blower unit.